astro-, astr-

The time between sunset or sunrise and the moment when the sun's center lies 18 degrees below the horizon.

1. The mean distance of the earth from the sun, which is 149,597,870 kilometers, or about 93 million miles.
2. A unit of length used by astronomers to measure distances in space.

One astronomical unit, or AU, is equal to the average distance between the earth and the sun, which is 92,955,806 miles or 149,597,870 kilometers.

1. A reference to astronomy or the scientific study of stars, planets, and other objects in outer space.
2. Referring to anything which is large in size or quantity: "The cost of health care has risen astronomically."

To study or to talk about astronomy.

1. The scientific study of matter in outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies and phenomena.

Astronomy literally means "law of the stars" or "culture of the stars"; depending on the translation, and it is derived from the Greek αστρονομία, astronomia, from the words άστρον, astron, "star" and νόμος, nomos, "laws" or "cultures".

2. The science that deals with the material universe beyond the earth's atmosphere.
3. The scientific study of the universe, especially of the motions, positions, sizes, composition, and behavior of astronomical objects.

These objects are studied and interpreted from the radiation they emit and from data gathered by interplanetary probes.

The average distance from earth to the sun; about 150 million kilometers.

Someone who is fond of star lore or the acquired knowledge or wisdom about stars: Mr. Jones, an astrophile, not only loved looking at the stars on clear nights, but also learned about the local traditions or myths of stars, handed down by word of mouth and usually in the form of stories or historical anecdotes.

A reference to someone who has a love or fondness for the stars: Lynn's principal at school was an astrophilic person who spent all of his vacations studying and observing at the heavenly bodies with his special telescope.

An excessive fear of stars and how they may have adverse influences on one's life or destiny: Since she was a child, Susan suffered from astrophobia and refused to go out when the night was dark and cloudless believing that she would be predestined to doom.

A reference to an excessive or morbid dread of stars and how they may have negative influences on one’s life or future destiny: Tim thought a lot about his job after completing his university education and decided to avoid going out at night because of his astrophobic anxieties which might affect his career in an adverse and destructive way.

Photography which is used in astronomical investigations.

Someone who specializes in a type of photography that entails making photographs of astronomical objects in the night sky; such as, planets, stars, and deep sky objects including star clusters and galaxies.

1. The art of photographing astronomical objects and events for astronomical studies>
2. The photography of stars and other celestial objects.
3. The use of photographs to record extraterrestrial objects in order to study their surface features, positions, motions, radiation, and spectra.

1. A photometer (light meter) for measuring the brightness of stars.
2. The measurement of the intensity of light of celestial objects.

Relating to the measurement of the intensity of light of celestial objects.